Impedance converters are used nowadays in particular in antenna arrangements for transformation of impedances. The impedance converters serve for matching the impedances resulting from individual radiator elements or antenna components, such as e.g. phase shifters, filters, bandpass filters, in broadband fashion to a common system impedance, which is 50 ohms in the field of mobile radio.
The prior art discloses impedance converters in which an impedance conversion is carried out by means of a λ/4 transformation by virtue of coaxial cables having a length corresponding to a quarter of the wavelength of the radio frequency with which the antenna arrangement is operated being interposed between connections in the antenna arrangement. In this case, it proves to be disadvantageous that, for the interposition of coaxial cables, a multiplicity of soldering points have to be provided at the ends of the coaxial cables, so that the production of such impedance converters is expensive and also greatly affected by tolerances owing to the diversity of parts. Equally, the prior art discloses tuning screws for altering the impedance in coaxial elements. This type of impedance conversion is also comparatively expensive. Moreover, impedance transformations are carried out by means of impedance converters in the form of strip conductors on circuit boards. What is disadvantageous in this case is that these impedance converters are permissible only for limited radio-frequency powers and a subsequent tuning of the impedance is not possible; in addition, intermodulation problems have to be reckoned with.
Therefore, it is an object of the exemplary illustrative non-limiting technology herein to provide an impedance converter device which can be produced cost-effectively, is suitable for high radio-frequency power and enables a tuning of the impedance in a simple manner.
The impedance converter device according to an exemplary illustrative non-limiting implementation herein is distinguished by a special shaping of an external conductor, of an internal conductor and also of a dielectric located in between. The external conductor of the device comprises a base area bounded by one or more side walls, thereby forming an external conductor housing with an internal space and an opening opposite the base area. The internal conductor is arranged in the internal space, the internal conductor and the external conductor being insulated from one another by the dielectric. The internal conductor comprises at least one cutoff bar-type section with a bottom and at least one wall which extends from the bottom in the direction of the opening of the external conductor housing. The configuration of the external conductor as an open housing enables access to the internal conductor, in particular to the walls of the cutoff bar-type sections. The angle of said walls can be adjusted by a corresponding tool, thereby enabling an operator to tune the impedance in a simple manner without intermodulation problems occurring or the intermodulation properties being impaired. It should be noted in this case that the opening can be closed by a suitable closure device. On the side opposite the base area of the exemplary illustrative non-limiting implementation, the housing is not formed in one piece with all the side walls of the housing, so that an (if appropriate also closed) opening can always be localized in the impedance converter. A further advantage of the exemplary illustrative non-limiting impedance converter is that the external conductor housing can be used universally and only the readily accessible internal conductor has to be exchanged in order to alter the transformation properties of the impedance converter. On account of the structural height attained by the external conductor housing, undesirable emissions of the converter do not occur. Moreover, the converter can be used for very high radio-frequency powers.
Preferably, the impedance converter essentially extends in a longitudinal direction between at least two opposite connection locations. Furthermore, at least web bottom of a cutoff bar-type internal conductor section is assigned at least two walls which extend in the direction of the opening of the external conductor housing in particular from edges of the bottom. In particular, the walls assigned to a bottom are parallel to one another. In one exemplary illustrative non-limiting implementation, the walls assigned to a bottom converge or diverge in the longitudinal direction of the impedance converter in a sectional view along a plane parallel to the base area of the external conductor. As an alternative, the walls assigned to a bottom are parallel to one another. Furthermore, the walls assigned to a bottom may be essentially perpendicular to the bottom. As an alternative, the walls assigned to a bottom diverge or converge in the direction of the opening of the external conductor housing in a sectional view along a plane perpendicular to the longitudinal direction of the impedance converter.
In an exemplary illustrative non-limiting implementation, the external conductor comprises a stamped, one-piece metal sheet with bent-over side walls. This enables the external conductor to be produced extremely inexpensively since the production by stamping is simple and cost-effective. Analogously, the internal conductor is preferably likewise a stamped, one-piece metal sheet with bent-over walls. This results, on the one hand, in cost-effective production of the internal conductor and, on the other hand, ensures good bendability of the walls, so that the impedance can easily be tuned or altered by bending the walls.
In an exemplary illustrative non-limiting implementation, the dielectric is a component with a receptacle, the component being inserted in the internal space of the external conductor housing and the internal conductor being arranged in the receptacle of the component. This results, in a simple manner, in an electrical insulation between internal conductor and external conductor by means of a separate component. In this case, the component is preferably formed in one piece. Furthermore, in a preferred variant, the component is held by force locking, in particular by a clamping, and/or by positive locking and/or by material locking in the external conductor housing. Analogously, the internal conductor may be held by force locking, in particular by a clamping, and/or by positive locking and/or by material locking in the receptacle of the dielectric. This enables simple assembly of the components of the impedance converter according to the exemplary implementation without the need to provide additional fixing means.
In a further preferred variant of the converter, the internal conductor has, at its ends, end sections with at least one or more end areas which extend in the direction of the opening of the external conductor housing. These end sections can be used to fix the position of the internal conductor in the external conductor housing. When this variant is combined with the exemplary implementation in which the dielectric is a component with a receptacle, one or more corners of the receptacle are preferably rounded and receive edges of the end sections of the internal conductor.
In an exemplary illustrative non-limiting implementation, the internal conductor has at least one first cutoff bar-type section for impedance transformation. In this case, the first cutoff bar-type section preferably has a length which is ¼ of the wavelength of a radio frequency which is used for mobile radio transmission, in particular a radio frequency in a GSM network and/or UMTS network. In this case, the length is preferably coordinated with the center frequency to be transmitted. This enables the impedance converter according to the exemplary implementation to be used as a λ/4 transformer in customary mobile radio networks. The impedance converter also makes it possible, if appropriate, to carry out multistage λ/4 transformations when using long external conductors.
In a further illustrative exemplary non-limiting implementation, the internal conductor has at least one second cutoff bar-type section for length adaptation of the internal conductor. The second cutoff bar-type section has the effect that the length of the internal conductor is always identical, independently of the radio-frequencies used, so that the internal conductor can always be inserted into an identically constructed external conductor housing. Consequently, the impedance converter can be adapted to different antenna systems in a simple manner by exchanging the internal conductor.
In order to connect the impedance converter to electrical lines, connection locations are provided in external conductor and in the internal conductor, said connection locations preferably comprising openings at ends of the external conductor and of the internal conductor, respectively. Each opening of the external conductor is preferably aligned with an opening of the internal conductor, the aligned openings in each case being connected to one another through an opening in the dielectric. The openings of the external conductor and of the internal conductor are preferably designed for receiving and subsequently soldering coaxial cables, the openings of the external conductor serving to receive a coaxial external conductor and the openings of the internal conductor serving to receive a coaxial internal conductor. The openings of the dielectric are preferably in each case accommodated in cutouts which serve in particular to receive an insulation arranged between a coaxial external conductor and a coaxial internal conductor. Furthermore, the openings of the external conductor may comprise at least one shoulder which serves in particular as a stop for an end of a coaxial external conductor.
In an exemplary illustrative impedance converter implementation, coaxial cables are soldered by means of soldering paste and/or integrated soldering moldings at the openings of the external conductor and of the internal conductor. This enables the coaxial cables to be soldered to the impedance converter in an automated and cost-effective manner.
In a refinement, the exemplary illustrative dielectric used in the impedance converter may comprise air, which means that the internal and external conductors of the impedance converter are spaced apart from one another by additional spacing means.
In a further refinement of the exemplary impedance converterimplementation, the internal conductor is configured in compartment-like fashion with a plurality of cutoff bar-type sections arranged parallel. This enables the device to be interconnected with a plurality of different systems. In order to fix the cutoff bar-type sections, the latter are in each case arranged in a cutout in the dielectric.